Running as administrator had no effect.
Editing graphicsSettings.lsx did not work, and the default values (800x600) were reset each game restart.
Fake fullscreen had no effect. Windowed neither - it appeared to run in 800x600 as well.
Switching to 1920x1080 as my display's resolution in Windows did work. This is undesirable though - 1920x1080 on a 27" screen is not pretty. I can not remember a non-ancient game that forced me to do that. Do you think it will be fixed?